1. Introduction
The present invention relates to a solution for treating copper and copper alloy. More specifically, this invention relates to a cleaning, deoxidizing and brightening solution for copper and copper alloys comprising sulfuric acid activated with hydrogen peroxide, low molecular weight ammonium compound and fatty acid amine. Aside from providing exceptional brightness, the solution of the present invention imparts considerable tarnish resistance to the copper or copper alloy surface treated.
2. Description of the Prior Art
The conventional methods employed for treating the surface of copper or copper alloys have included both mechanical and chemical techniques. Mechanical methods such as buff-polishing and barrel-polishing have a disadvantage of requiring a number of steps and a fair degree of experience. Furthermore, using such methods, it is difficult to obtain a uniform, lustered surface, and in many cases, depending on the size or form of the articles to be treated, polishing is difficult or even impossible.
Chemical methods, such as those wherein a mixture of acids, composed of for example, sulfuric, nitric, and a small amount of hydrochloric acid, is employed, has similarly not been entirely satisfactory. Not only is experience required in carrying out the operation, using such a mixture, but the operation itself is hazardous due to evolution of poisonous nitrous oxide fumes during the process of polishing. This is considered to be a serious drawback of this conventional method. In addition, when this method is employed, pitting, irregularity of color, change of color after polishing and the like are likely to occur. At the same time the method requires the use of concentrated nitric and sulfuric acids, the danger accompanying such use is apparent.
Other chemical methods involve the use of chromic acid in addition to the above-described acids. A major disadvantage of a solution of this type is that chromic acid is highly toxic requiring meticilous waste treatment which further adds to the cost of the cleaning, deoxidizing and brightening operation.
Other conventional methods employ the use of hydrogen peroxide with an acid or acids. Such methods are greatly restricted in regard to the temperature, concentration of the hydrogen peroxide and the concentration of acids to be employed in order to obtain the desired result. Furthermore, a major disadvantage of this method is that the stability of the hydrogen peroxide markedly deteriorates after copper is disolved to some extent during the cleaning, deoxidizing and brightening operations. The useful life of the solution is therefore remarkably short. It is believed that the reason is that heavy metal ions interfere and affect the stability of hydrogen peroxide. Because of these disadvantages, a pratical method for chemically treating the surface of copper and copper alloys with hydrogen peroxide has not been available. Although various stabilizing agents have been added to hydrogen peroxide type solutions, the above-described disadvantages in combining various types of acids still exists.